This invention describes an imaginative new shoe design based on the principle of energy conversion. The inventive shoe will make running smoother, easier, more efficient, quicker, and simultaneously will reduce injuries arising from impact forces.
All runners fit in two simple categories, those who land on their heels and those who land on their toes.
Heel runners: These, known also as "heel strikers", land on the back portion of their heel, roll forward on the outer side of the foot, and push off from the toe-forefoot area. The "striking" occurs in a relatively small region at the rear and outside of the heel. The impact of force or pressure of landing is calculated in pounds per square inch. That is, the weight of the runner multiplied by the impact area in square inches (small; say one half by one inch). The resulting impact pressure or force is large, often awesome. Since the descent of the foot on hitting the ground stops abruptly, in fact almost instantaneously, the law of "equal opposite forces" dictates that an equal pressure or force is transmitted in the opposite direction, back up the leg from foot to ankle to knee to hip. Taken over time, this jolt in distance runners (30 miles or more a week) causes predictable wear and tear problems involving foot, ankle, knee, hip and even back. This is the source of most injuries in distance runners. In addition, most "heel strikers" land with center of gravity slightly behind the point of impact, hence some of the reactive force up the leg actually pushes them backward. The runner locks the knee and "pogo-sticks" over the foot before rolling forward to the push-off position. This is inefficient, wasteful of energy, and tiring while causing a small though real slowing of the runner's forward progress.
Toe Runners: The other, smaller group of runners land on their toes or actually their forefoot areas. The point of impact is more apt to be under or modestly behind their center of gravity. The knee is slightly bent and absorbs some reactive energy. This style propels the runner forward, is more efficient, less tiring, and less prone to injuries. This group tends to be the sprinters and the elite distance runners.
All shoes are basically the same. Tops to cover the foot and keep the bottoms in place. Bottoms to protect the sole and to provide cushioning to absorb impact pressures.
Over recent years, shoe manufacturers have developed a variety of materials to reduce impact pressures through principles of compression and dispersion to absorb energy. Thus, modifications in design and composition of the heels (sponges, inserts, treads, air, and gels) and forefoot (sponges, inserts, and treads). All shoes employ the same principles with only a variation in theme. Thus the following:
U.S. Pat. No. 4,616,335 describes an athletic shoe structure including shock absorbing portions in the heel and foot areas of the sole of the shoe as well as particular placement of flexible nubs on the soft area.
U.S. Pat. No. 4,348,821 is directed towards the development of a shoe sole construction that will be mechanically effective for walking, running or jogging.
U.S. Pat. No. 4,262,435 is directed to an improved athletic shoe and with the sole piece as a wedge to facilitate supporting the runner's foot when contacting the ground.
Today, there is a need to make the shoe better by incorporating the concept of "conversion" in the design of the shoe. No shoe to date employs the principle of energy conversion.